SEWAGE HARVESTING FOR URBAN GREEN IRRIGATION LET2009 Singapore.pdf · !a sedimentation tank to...
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SEWAGE HARVESTING FOR URBAN GREEN IRRIGATION * ** ** Karl-Ulrich Rudolph , Stefania Paris , Franz Heindl Background First Results Conclusions The authors would like to thank the German Federal Ministry of Education and Research for sponsoiring the research work (FKZ: ) 02WD0757 and 02WD0759 In arid urban areas public green areas like parks or road medians are essential for life as they positively influence the local climate and reduce the appearance of dust. Even in regions with scarce water resources, mostly potable water from public water supply systems is used to irrigate these areas, resulting in an increasing lack of water for higher-valuable uses. On the other hand, particularly in arid developing countries, completely uncontrolled use of raw wastewater for irrigation purposes is widely spread, with all the hygienic problems linked to this. Approach To improve the situation, a concept for controlled utilisation of wastewater from existing sewage systems as irrigation water has been developed. Aim of the project is not to offer a costly full purification facility for the sewage but a comparatively efficient system with partial treatment and disinfection of raw wastewater, only as far as it is necessary for the specific use in urban green spaces. Reduction of organics and nutrients by biological treatment is of minor relevance in this specific case, as nutrients often can be utilised as fertiliser. Main objective with wastewater reuse for public spaces is appropriate disinfection. Therefore, as key element of a multi-barrier strategy, the technical treatment concept can be focused on the mechanical purification and disinfection of the raw wastewater. A preliminary survey on different disinfection options has shown UV irradiation to be the most appropriate disinfection technology in this context. First lab scale tests offered promising results, indicating that feasible disinfections rates to fulfil WHO standards for non-food irrigation are achievable with UV doses being three times higher for only partly treated wastewater than for fully purified wastewater (typically 400 J/m²), which is still economically reasonable in terms of energy consumption. The practical tests also underpin the need for a well-considered adjustment of the treatment components and their configuration within the overall system, as for example the treatment by the pipe strainer changes the particle composition with effects on the UV disinfection efficiency. Multi-barrier strategy To control hygienic risks through irrigation of urban areas with only partly purified wastewater, a multi-barrier strategy has been outlined, including three principal aspects: 1) The kind of reutilization has to be suitable for the site conditions (considering the geological situation, plantings, etc.). 2) The way of handling has to be suitable for the water reutilization (considering the distribution and application of the irrigation water). 3) The type of treatment has to be suitable to the way of handling of sewage (considering especially the reduction of pathogens). By this, the technological concept is only one element of the overall approach. Principle of the pipe strainer Screening zone Discharge section Modified scheme with partial treatment Disinfection Fine Screen Sedimentation tank In Out Modified scheme with partial treatment Disinfection Fine Screen Sedimentation tank In Out Disinfection Conventional treatment scheme Screen Grit chamber Biological treatment Final Clarifier Filtration In Out Disinfection Conventional treatment scheme Screen Grit chamber Biological treatment Final Clarifier Filtration In Out Technological concept To make it reliable for decentralised applications, the treatment unit should be very compact, robust and mobile. The developed consists of only four elements (see general scheme on the left): ! A pump to feed the system with raw sewage from existing sewage systems, ! a mechanical separation of solid wastes by a pipe strainer, ! a sedimentation tank to reduce the suspended solids, ! a following disinfection unit with UV irradiation. Within the still ongoing research project, a compact system has been developed for an efficient decentralised reuse of wastewater from existing sewage systems for irrigation of green areas in arid regions. First results indicate that the relatively simple system concentrated on mechanical treatment and disinfection could be a helpful component to reduce the use of potable water for irrigation purposes in these regions. * Institute of Environmental Engineering and Management Alfred-Herrhausen-Str. 44 | 58455 | Witten | Germany +49 2302 91401-0 | www.uni-wh-utm.de ** Hans Huber AG Industriepark Erasbach A1 | 92334 Berching | Germany +49 8462 201-744 | www.huber.de
Transcript of SEWAGE HARVESTING FOR URBAN GREEN IRRIGATION LET2009 Singapore.pdf · !a sedimentation tank to...
SEWAGE HARVESTING FOR URBAN GREEN IRRIGATION* ** **Karl-Ulrich Rudolph , Stefania Paris , Franz Heindl
Background
First Results
Conclusions
The authors would like to thank the German Federal Ministry of Education and Research for sponsoiring the research work (FKZ: )02WD0757 and 02WD0759
In arid urban areas public green areas like parks or road medians are essential for life as they positively influence the local climate and reduce the appearance of dust. Even in regions with scarce water resources, mostly potable water from public water supply systems is used to irrigate these areas, resulting in an increasing lack of water for higher-valuable uses.
On the other hand, particularly in arid developing countries, completely uncontrolled use of raw wastewater for irrigation purposes is widely spread, with all the hygienic problems linked to this.
ApproachTo improve the situation, a concept for controlled utilisation of wastewater from existing sewage systems as irrigation water has been developed. Aim of the project is not to offer a costly full purification facility for the sewage but a comparatively efficient system with partial treatment and disinfection of raw wastewater, only as far as it is necessary for the specific use in urban green spaces.
Reduction of organics and nutrients by biological treatment is of minor relevance in this specific case, as nutrients often can be utilised as fertiliser. Main objective with wastewater reuse for public spaces is appropriate disinfection. Therefore, as key element of a multi-barrier strategy, the technical treatment concept can be focused on the mechanical purification and disinfection of the raw wastewater.
A preliminary survey on different disinfection options has shown UV irradiation to be the most appropriate disinfection technology in this context. First lab scale tests offered promising results, indicating that feasible disinfections rates to fulfil WHO standards for non-food irrigation are achievable with UV doses being three times higher for only partly treated wastewater than for fully purified wastewater (typically 400 J/m²), which is still economically reasonable in terms of energy consumption.
The practical tests also underpin the need for a well-considered adjustment of the treatment components and their configuration within the overall system, as for example the treatment by the pipe strainer changes the particle composition with effects onthe UV disinfection efficiency.
Multi-barrier strategyTo control hygienic risks through irrigation of urban areas with only partly purified wastewater, a multi-barrier strategy has been outlined, including three principal aspects:
1) The kind of reutilization has to be suitable for the site conditions (considering the geological situation, plantings, etc.).
2) The way of handling has to be suitable for the water reutilization (considering the distribution and application of the irrigation water).
3) The type of treatment has to be suitable to the way of handling of sewage (considering especially the reduction of pathogens).
By this, the technological concept is only one element of the overall approach.
Principle of the pipe strainer
Screening zone
Discharge section
Modified scheme with partial treatment
DisinfectionFineScreen
Sedimentationtank
In Out
Modified scheme with partial treatment
DisinfectionFineScreen
Sedimentationtank
In Out
Disinfection
Conventional treatment scheme
Screen Grit chamber Biologicaltreatment
Final Clarifier
Filtration
In Out
Disinfection
Conventional treatment scheme
Screen Grit chamber Biologicaltreatment
Final Clarifier
Filtration
In Out
Technological conceptTo make it reliable for decentralised applications, the treatment unit should be very compact, robust and mobile. The developed consists of only four elements (see general scheme on the left):
! A pump to feed the system with raw sewage from existing sewage systems,
! a mechanical separation of solid wastes by a pipe strainer,
! a sedimentation tank to reduce the suspended solids,
! a following disinfection unit with UV irradiation.
Within the still ongoing research project, a compact system has been developed for an efficient decentralised reuse of wastewater from existing sewage systems for irrigation of green areas in arid regions. First results indicate that the relatively simple system concentrated on mechanical treatment and disinfection could be a helpful component to reduce the use of potable water for irrigation purposes in these regions.
* Institute of Environmental Engineering and Management
Alfred-Herrhausen-Str. 44 | 58455 | Witten | Germany
+49 2302 91401-0 | www.uni-wh-utm.de
** Hans Huber AG
Industriepark Erasbach A1 | 92334 Berching | Germany
+49 8462 201-744 | www.huber.de
